1. Technical Field
The present invention relates to a MEMS vibrator and an oscillator.
2. Related Art
MEMS (Micro Electro Mechanical Systems) are one of techniques for forming a minute structure.
JP-A-2010-162629 discloses a MEMS vibrator having a fixed electrode and a movable electrode, in which a cantilever movable electrode is driven by electrostatic force generated between the electrodes. An output of such a cantilever electrostatic MEMS vibrator is generated by a change in capacitance between the fixed electrode and the movable electrode when driven. Therefore, the larger the crossing area of the fixed electrode and the movable electrode (the area of a region where the electrodes overlap each other) is, the higher the output is.
On the other hand, a driving frequency is a natural frequency of a vibrator, and determined by the shape and dimensions of the vibrator. Various shapes of MEMS vibrators driven in a frequency band from several kHz to several GHz have been proposed so far. In the case of the MEMS vibrator having a cantilever structure disclosed in JP-A-2010-162629, the driving frequency is determined by the length and thickness of a beam portion (movable electrode). When the thickness is constant, the great length of the beam portion makes the frequency low, and the small length makes the frequency high.
In this manner, since the frequency of the MEMS vibrator depends on the shape of its beam portion, high processing accuracy is required in manufacturing processes of the MEMS vibrator.
However, in the manufacturing processes of the MEMS vibrator, since the fixed electrode and the movable electrode are formed in different processes, an error occurs in a positional relation between them. That is, since an error occurs in the beam length and the crossing area, a desired frequency cannot be obtained in some cases, making the frequency accuracy low.